Location Of Target Object Research Articles

Attending to Remember and Remembering to Attend

Attention and memory are intimately linked. Two functional imaging studies in this issue of Neuron provide novel evidence for this powerful, reciprocal relationship. Turk-Browne and colleagues report that attention simultaneously facilitates the formation of both implicit and explicit memories, while Summerfield and colleagues demonstrate that memory for the past can guide the allocation of attention in the present. Together, these elegant studies reveal bidirectional interactions between attention and memory.

Navigation Fidelity in 3D Perspective Displays for Web-Based Shopping: From Nodes to Views

To assess its usefulness as a Web navigation-aiding metaphor, a virtual Euclidean space was created that participants (N = 96) navigated to find information in a Web shopping environment. Acquisition of configural-survey 3-dimensional (3D) spatial knowledge of the environment, measured with pointing and sketch map tasks, was compared using perspective displays of virtual environments created using Hypertext Markup Language (HTML) versus a 3D graphics engine. HTML navigation fidelity was manipulated by varying the turn angles and the number of viewpoints per store. Lower navigation fidelity reduced configural knowledge acquisition, but HTML store environments using 45�-turn angles and 9 viewpoints per store were not reliably different from the 3D virtual environment generated by a graphics engine with optical flow. Target object location (within-store, between-store) also had a significant effect. The results indicate that HTML could be used to develop virtual Web shopping environments using discrete perspective displays. Implications for Web shopping interface design are discussed.

Rotational movements in real and virtual environments

The study compared spatial learning in real and virtual small-scale environments. Twenty-four participants were placed in the center of laboratory and equivalent virtual environments. The participants’ task was to learn the location of target objects by turning left or right using rotational movements only. Knowledge of the location of the targets was subsequently assessed in pointing and map tasks. The main finding was comparable pointing performance following real and virtual learning. Increasing the amount of practice decreased pointing errors, and augmenting the environments with cardinal reference directions resulted in a reduction in error scores. The results suggest that learning through rotational movements is relatively unaffected by lack of vestibular feedback.

Rotational movements in real and virtual environments

Abstract The study compared spatial learning in real and virtual small-scale environments. Twenty-four participants were placed in the center of laboratory and equivalent virtual environments. The participants’ task was to learn the location of target objects by turning left or right using rotational movements only. Knowledge of the location of the targets was subsequently assessed in pointing and map tasks. The main finding was comparable pointing performance following real and virtual learning. Increasing the amount of practice decreased pointing errors, and augmenting the environments with cardinal reference directions resulted in a reduction in error scores. The results suggest that learning through rotational movements is relatively unaffected by lack of vestibular feedback.

3次元空間内の複数の仮想物体を提示するための遭遇型ハプティックデバイスの軌道計画

A path-planning algorithm for encountered-type haptic devices that render multiple virtual objects in 3D space is proposed. To render multiple virtual objects with a single haptic device, the following two behaviors must be realized: (i) the device should move to the target object location in advance of the user's hand so that the user can encounter it; (ii) otherwise, the device should keep away from the user's hand, avoiding an unexpected collision. To realize such a consistent encounter, the user's hand motion must be tracked. The proposed algorithm determines the device location based on the minimum distance problem between a point (the user's hand) and a convex polyhedron constructed from the reference points of multiple objects. An automobile virtual control panel was constructed using an encountered-type haptic device in which the proposed path-planning algorithm was implemented. The validity of the proposed algorithm was confirmed and the required performances, such as the device speed and the accuracy of hand tracking were evaluated.

An active contour model with shape regulation scheme

This paper presents an active method for locating target objects in images, which is aimed at improving the performance of detecting object boundaries by enhancing the behavioral characteristics of an active contour. The proposed active contour model simulates a mechanical system consisting of two main parts: the first is a rigid fixture, called the 'core', specifying the expected shape of target boundaries, while the second is an elastic rod attached to the rigid fixture. The elastic rod deforms or moves relative to the rigid core according to the classical laws of the mechanical system. When the initial contour is applied to an image data, it is attracted near the dominant image features, but tries to keep its home shape and simultaneously make the deformation smooth if a deformation is more natural for force equilibrium. This mechanism significantly improves the performance of detecting object boundaries in the presence of some disturbing image features. The active contour is scale invariant, thereby significantly relieving the difficulty in selecting proper values for the model parameters. The values for the model parameters can be selected to make the contour have the desired behaviors around the equilibrium position through the analysis of the vibration mode of the mechanical system. The performance of the proposed method is validated through a series of experiments, which include detection of heavily degraded objects, tracking of objects under non-rigid motion and comparisons with the original snake models.

The reach-to-grasp movement in Parkinson's disease: response to a simultaneous perturbation of object position and object size.

This study assessed the adaptive response of the reach-to-grasp movement of 12 Parkinson's disease (PD) and 12 control subjects to a simultaneous perturbation of target object location and size. The main aim was to test further the reported dysfunction of PD subjects in the simultaneous activation of movement components. Participants were required to reach 30 cm to grasp a central illuminated cylinder of either small (0.7 cm) or large (8 cm) diameter. For a small percentage of trials (20/100) a visual perturbation was introduced unexpectedly at the onset of the reaching action. This consisted of a shift of illumination from the central cylinder to a cylinder of differing diameter, which was positioned 20 degrees to the left (n = 10) or to the right (n = 10). The subject was required to grasp the newly illuminated cylinder. For the Parkinson's disease subject group, the earliest response to this 'double' perturbation was in the parameter of peak reaching acceleration, which was on average 50 ms earlier for 'double' perturbed than for non-perturbed trials. The grasp component response followed more than 500 ms after the earliest transport response. For the control subjects initial signs of a response to the 'double' perturbation were seen almost simultaneously in the transport parameter of peak arm deceleration, and in the manipulation parameter of maximum grip aperture, but these changes were not evident until more than 400 ms after movement onset. These results indicate that the basal ganglia can be identified as part of a circuit which is involved in the integration of parallel neutral pathways, and which exercise flexibility in the degree to which these components are 'coupled' functionally. With basal ganglia dysfunction the activation of integration centres that at first gate the flow of information to the parallel channels of reach and grasp seems inefficient.

Object-based attentional selection--Grouped arrays or spatially invariant representations?: Comment on Vecera and Farah (1994).

S. P. Vecera and M. J. Farah (1994) have addressed the issue of whether visual attention selects objects or locations. They obtained data that they interpreted as evidence for attentional selection of objects from an internal spatially invariant representation. A. F. Kramer, T. A. Weber, and S. E. Watson question this interpretation on both theoretical and empirical grounds. First, the authors suggest that there are other interpretations of the Vecera and Farah data that are consistent with location-mediated selection of objects. Second, they provide data, using the displays employed by Vecera and Farah in conjunction with a postdisplay probe technique, that suggests that attention is directed to the locations of the target objects. The implications of the results for space and object-based attentional selection are discussed.

Reference systems for coding spatial information in normal subjects and a deafferented patient

To produce accurate goal-directed arm movements, subjects must determine the precise location of target object. Position of extracorporeal objects can be determined using: (a) an egocentric frame of reference, in which the target is localized in relation to the position of the body; and/or (b) an allocentric system, in which target position is determined in relation to stable visual landmarks surrounding the target (Bridgeman 1989; Paillard 1991). The present experiment was based on the premise that (a) the presence of a structured visual environment enables the use of an allocentric frame of reference, and (b) the sole presence of a visual target within a homogeneous background forces the registration of the target location by an egocentric system. Normal subjects and a deafferented patient (i.e., with an impaired egocentric system) pointed to visual targets presented in both visual environments to evaluate the efficiency of the two reference systems. For normals, the visual environment conditions did not affect pointing accuracy. However, kinematic parameters were affected by the presence or absence of a structured visual surrounding. For the deafferented patient, the presence of a structured visual environment permitted a decrease in spatial errors when compared with the unstructured surrounding condition (for movements with or without visual feedback of the trajectory). Overall, results support the existence of an egocentric and an allocentric reference system capable of organizing extracorporeal space during arm movements directed toward visual targets.

Enhancement of 3-D Video Displays by Means of Superimposed Stereo-Graphics

This paper describes a number of aspects of a display technology under development, which involves the integration of stereoscopic computer graphics and stereoscopic video displays. The background and justification for this development are discussed, based on the need of operators of remotely controlled vehicles and/or manipulators to estimate absolute sizes and locations of objects at a remotely viewed site. The basic technology involves superimposing an interactively controllable computer-generated stereographic cursor onto a stereoscopically viewed video image. Absolute measurements can be made with this system, based on relative comparison of cursor position with target object location. Experimental results are presented in which the ability of subjects to perform such tasks was investigated. In general, results were promising; subjects were able to align virtual pointers with real targets essentially as well as they were able to manipulate real objects. A number of implications of this technology for the enhancement of three dimensional video displays are discussed.

The timing of natural prehension movements.

Prehension movements were studied by film in 7 adult subjects. Transportation of the hand to the target-object location had features very similar to any aiming arm movement, that is, it involved a fast-velocity initial phase and a low-velocity final phase. The peak velocity of the movement was highly correlated with its amplitude, although total movement duration tended to remain invariant when target distance was changed. The low-velocity phase consistently began after about 75% of movement time had elapsed. This ration was maintained for different movement amplitudes. Formation of the finger grip occurred during hand transportation. Fingers were first stretched and then began to close in anticipation to contact with the object. The onset of the closure phase was highly correlated to the beginning of the low velocity phase of transportation. This pattern for both transportation and finger grip formation was maintained in conditions whether visual feedback from the moving limb was present or not. Implications of these findings for the central programming of multisegmental movements are discussed.

Mandatory Processing of the Background in the Detection of Objects in Scenes

Would the relationships between an object and its real-world setting affect the detectibility of that object even when the observer knew what the object was and where it would appear? Mandatory processing of scene backgrounds was investigated using a pre-cue design in which the target object's name and location was supplied to the subject prior to a single 100 msec. presentation of a line drawing of a real-world scene. The deleterious effect of violating relationships between the target and background indicated that the processing of the scene background was mandatory and affected the perceptability of the target rather than the memory of the scene.